Perched Water Tables on Argixeroll and Fragixeralf Hillslopes

Abstract

Seasonally perched water tables (PWTs) are common in loess‐derived Argixerolls and Fragixeralfs of the Palouse region of northern Idaho and eastern Washington. However, little is known about the short‐term PWT dynamics in these rolling to hilly landscapes and how they are influenced by a regional climatic gradient. In this study, PWTs on an Argixeroll hillslope receiving 700 mm of mean annual precipitation (MAP) and a Fragixeralf hillslope receiving 830 mm of MAP were monitored hourly for four seasons. Results demonstrate that timing of PWT formation may vary considerably from year to year, and may occur up to 3 wk earlier in Fragixeralfs than in Argixerolls. Once formed, the PWTs respond rapidly to precipitation and snowmelt in both soils, with PWT levels increasing as much as 60 cm within a period of <24 h. Water table levels are at or near the soil surface numerous times during the season following periods of rainfall or snowmelt. Perched water table dynamics are remarkably consistent across the region, with similar responses observed in hillslopes located 28 km apart. Relatively dense, light‐colored E horizons overlying the restrictive horizons remain continuously saturated for up to 6 to 7 mo yr−1 and develop redox potentials sufficiently low for Fe reduction to occur. Results suggest that seasonal PWTs drive the processes of ferrolysis and hydroconsolidation, and these processes are responsible for many of the E horizon properties common to Argixerolls and Fragixeralfs of the region.

Impact of Climate Change Adaptation Strategies on Winter Wheat and Cropping System Performance across Precipitation Gradients in the Inland Pacific Northwest, USA

“…Furthermore, topographic complexity varies across the region leading to differences in soil properties (Horner et al, 1957). As precipitation increases, the presence of finer-textured silty-clay and clay-loam soils with dense (∼1.65 Mg m −3 ) argillic and fragipan horizons at depths from 0.2 to 1.2 m below the soil surface can restrict vertical drainage and root penetration leading to the development of seasonal perched water tables (McDaniel et al, 2001;Brooks et al, 2012). These argillic and fragipan soils are generally found where mean annual precipitation exceeds 600 mm and have a limited soil water holding capacity due to the presence of dense subsurface clays (Brooks et al, 2012).…”

Groundwater recharge in Pleistocene sediments overlying basalt aquifers in the Palouse Basin, USA: modeling of distributed recharge potential and identification of water pathways

“…The Palouse Formation loess overlies the Sediments of Bovill (Busacca and McDonald 1994). Poorly permeable or impermeable argillic layers or fragipans exist within the loess (McDaniel et al 2001), and elevation ranges from 767 to 1,327 m + A.S.L. Average annual precipitation (P) varies directly with elevation, ranging from 653 mm yr -1 at the lowest to 1,020 mm yr -1 at the highest elevation according to 800-m resolution PRISM (parameter-elevation regressions on independent slopes model) maps (PRISM 2009).…”

“…The nearly impermeable argillic soils (e.g. Southwick and Taney) and thick clay layers within the Sediments of Bovill act as restrictions to vertical water flow and lead to downslope lateral flow (McDaniel et al 2001), which redirects water to alluvial soils. Recharge pathways in PC watershed are initiated predominantly below non-argillic soils and soils not underlain by the Sediments of Bovill.…”

Hydrological versus biogeochemical controls on catchment nitrate export: a test of the flushing mechanism

“…Recent studies have highlighted the role of denitrification in the removal of NO 3 from near-stream zones, once the groundwater table has reached the ground surface (Faulkner and Patrick, 1992;McDaniel et al, 2001). Given likely anoxic conditions in the soil solution, denitrification would be promoted, thus removing NO 3 from the soil, as N 2 , and resulting in reduced stream NO 3 discharge.…”